1. Field of the Invention
This invention generally relates to rigid solid lubricant composite materials which are extremely heat-resistant and are moldable and thermosetting, and comprised of an organic silicone resin having a finely-ground particulate filler therein. The composition is formed by taking an organopolysiloxane resin or mixture of such resins in a solvent, and dispersing a prescribed amount of finely-ground graphite-containing material therein, the combined materials being able to be molded into a rigid thermoset, heat-resistant solid-lubricant material adapted to handling hot glass articles. The molding composition may be molded into products having precisely-sized and shaped contours prior to heat-curing the shaped product containing the resin and filler material.
The composite molding composition may be molded into a wide variety of products for long-term handling of newly-formed, hot glass articles without marring their surfaces or creating objectionable emissions from the composite material due to excessive heat. The molding composition cures into a thermoset hardened condition with strengthening chopped glass fibers fully dispersed throughout. The molded products possess an appreciable degree of heat-resistance, and can be employed alone without any additional heat-resistant fluid or solid coating applied to their exterior surfaces for long-term, repeated use in handling of hot glass articles.
2. Description of the Prior Art
It has been common practice in the glass-forming art to fabricate or cover conveyor belting and hot glass transfer mechanisms for transporting hot glass articles with asbestos or asbestos-containing composite materials such as transite to provide heat-resistant surfaces which would not mar the glass and provide long-term operating life. Conveyor mechanisms, such as sweepout arms, curved chain members, lehr bars, takeout tongs, and the like, have required high-temperature resistant materials on their glass contacting surfaces. Also, bucket liners and sweep arm fingers have previously been fabricated with coverings of asbestos cloth for handling hot glass articles. It is desirable to eliminate the use of all asbestos and cloth coverings in such operations.
In the production of glassware, certain handling equipment has also been coated with graphite and petroleum oil swabbing compounds to provide lubricity and heat-resistance. In the use of such coatings, when the petroleum fraction flashes off, it can detract from effective lubrication during forming and emit undesirable emissions into the surrounding atmosphere.
The use of water-based carriers instead of the petroleum oil carriers for graphite and other lubricious materials have not been entirely satisfactory, primarily due to the high heat of varporization of water, and the resulting excessive cooling of the glass-handling equipment. In addition, it is difficult to controllably wet the handling equipment surfaces with water-based materials which are applied intermittently during production of glassware.
High temperature fabrics based on inorganic fibers, such as glass, silica, quartz, and ceramics, have been proposed as replacement materials for asbestos and high-temperature resistant parts for handling hot glass articles up to 1000.degree. F. (538.degree. C.). In glass manufacturing operations, such fabrics do not normally stand up well in long-term repeated contact with hot glass articles because of their low resistance to abrasion. In the manufacture of glass fibers, for example, chemical treatments (sizings) such as acrylic resin or starch coatings are used to reduce abrasion contact and fiber breakage during processing. These are organic and burn off in a high temperature environment, such as when handling hot glass articles, resulting in surface abrasion at the product/fabric interface and also within the fabric. Fabrics based on inorganic fibers exhibit the necessary heat-resistance for hot glass handling; however, such materials require a combination with high temperature solid lubricant coating technology to be functional. Both U.S. Pat. No. 4,246,313 to Stengle, issued Jan. 20, 1981, entitled, "Heat-Resistant Composite Material and Method of Making Same", and U.S. Pat. No. 4,110,095 to Stengle, issued August 1978, entitled, "Manufacture of Glass wherein Hot Metal Molds are Provided With a Solid Film Lubricant Layer", relate to handling hot glass, the former subsequent to and the latter during formation of hollow glass containers, and both are assigned to the same common assignee as the present application.